1. Field of the Invention
The present invention relates to a thin-film magnetic head which performs magnetic recording operation by a perpendicular recording system, a method of manufacturing the same, a head gimbal assembly and hard disk drive.
2. Related Background Art
Surface recording densities in hard disk drives have improved dramatically in recent years. More particularly, surface recording densities in hard disk drives have recently reached 160-200 Gbytes/platter, and are poised to exceed even this level. At the same time, there has been a demand for improved performance of thin-film magnetic heads.
Thin-film magnetic heads are largely classified based on their recording systems, which may be divided into longitudinal recording systems wherein information is recorded in the (longitudinal) direction within the recording surface of the hard disk (recording medium), and perpendicular recording systems wherein the orientation of recording magnetization formed on the hard disk is formed in the perpendicular direction of the recording surface to record data. Of these types of systems, perpendicular recording type thin-film magnetic heads are capable of realizing markedly higher recording density than longitudinal recording systems, while they also are less susceptible to thermal fluctuation of the recorded hard disk, and are therefore more promising than longitudinal recording systems.
Conventional perpendicular recording type thin-film magnetic heads are disclosed, for example, in U.S. Pat. Nos. 6,504,675, 4,656,546,4,672,493 and Japanese Unexamined Patent Publication No. 2004-94997.
Incidentally, when thin-film magnetic heads of perpendicular recording systems accomplish recording of data in the inner and outer perimeters of hard disks, the magnetic pole tip situated on the side of the medium-opposing surface (also referred to air bearing surface, or ABS), which opposes the recording medium (hard disk), forms an angle (skew angle) with the data recording track. When the writing performance is high with a perpendicular recording type magnetic head (perpendicular magnetic recording head: hereinafter also referred to as “PMR”), this skew angle is responsible for a problem of side fringe, whereby excess data is recorded between adjacent tracks. When side fringe occurs, it can adversely affect detection of the servo signal, or the S/N ratio of the reproduction waveform. Conventional PMRs therefore have a bevel shape wherein the magnetic pole tip on the ABS side of the main pole gradually narrows in width toward one direction. (In this regard, see Japanese Unexamined Patent Publication No. 2003-242607 and Japanese Unexamined Patent Publication No. 2003-203311.)